The objective of this research project is to assess how the addition of a low-frequency acoustic signal to an electrical signal (i.e., a hearing aid in opposite ear to a cochlear implant) affects the processing of speech in cochlear implant recipients. Previous research has shown that the limited spectral cues provided by a cochlear implant results in poor speech recognition in noisy environments and prevents successful voice identification. The first aim of this project is to determine how the use of bimodal stimulation affects the identification of isolated vowels, voice-gender and the dialect of individual talkers. Three groups of study participants (i.e., unilateral cochlear implant recipients, bilateral cochlear implant recipients, and individuals using both a hearing aid and a cochlear implant) will complete tests that assess: 1) speech perception abilities in noise, 2) voice-gender identification and dialect discrimination/categorization, and 3) vowel recognition. The second aim is to assess the effects of bimodal stimulation on phonological memory capacity for acoustically distinct and acoustically similar vowels, and determine how individual working memory skills affect talker recognition. For this aim, study participants will be asked to recall short lists of isolated vowels that are either phonologically similar or phonologically dissimilar. The findings from these process measures will be compared with the findings from the Aim I studies to assess the contribution of phonological working memory in speech perception. It is expected that the results from this study will establish the importance of continued hearing aid use following cochlear implantation. Additionally, the findings from this study will provide the direction for future advances in cochlear implant technology related to improving the coding of the fine structure of speech. These technological advances will ultimately improve the speech perception abilities of cochlear implant recipients. This research is designed to establish links between individual discrimination abilities and immediate phonological memory skills in speech perception. Consequently, this research will contribute additional knowledge about the underlying basis for the individual variability in outcome performance that is widely observed within the cochlear implant population. [unreadable] [unreadable] [unreadable]